The field of this disclosure relates generally to sensors and, more particularly, to a temperature sensing device for a combustion section of a gas turbine engine.
Exhaust gas temperature in the combustion section of a gas turbine engine is an operating parameter that is often used by the engine control unit to determine fuel input to the combustor. As such, accurate measurements of the exhaust gas temperature within the combustor can facilitate improved operating efficiency of the engine by enabling optimized fuel inputs. Additionally, engine components within, and downstream of, the combustion section (e.g., turbine blades) are typically exposed to significant thermal stresses associated with the higher temperature of the exhaust gases, and the useful life of these downstream components is often estimated using expected exhaust gas temperatures in the combustor. Therefore, accurate measurements of the exhaust gas temperature can facilitate making the expected exhaust gas temperatures more accurate and, as a result, facilitate making the component life estimations more accurate as well.
At least some known exhaust gas temperature (EGT) sensors used in gas turbine engines include a thermocouple element. However, in order to have a higher reactance, these thermocouple elements often have smaller diameters. In that regard, exhaust gases within the engine can reach velocities of at least 240 m/s, and these smaller diameter thermocouple elements typically do not have enough rigidity to resist the drag associated with the exhaust gas flow velocity. As a result, some known EGT sensors have thermocouple elements that are disposed within a more rigid housing to provide increased support to withstand the associated drag, and most of these housings are fabricated from higher temperature rated alloys. However, the exhaust gases can reach temperatures of at least 2300° F. As a result, most known EGT sensors are inserted downstream of the combustor in areas where exhaust gas temperatures are below the service limit of the alloy housings (e.g., a few stages into the high-pressure turbine), and the downstream temperature measurements are used to estimate temperatures of the exhaust gases in the combustor. These estimated exhaust gas temperatures are then used by the engine controller to determine fuel input parameters for the combustor. Thus, to improve the accuracy of exhaust gas flow temperature measurements, it would be desirable to have a temperature sensing device that can be inserted directly into higher temperature locations within the exhaust gas flow of the combustor.